Date: Wed, 27 Mar 2002 16:51:45 -0500 (EST) From: John Baldwin <jhb@FreeBSD.org> To: Alfred Perlstein <alfred@FreeBSD.org> Cc: current@FreeBSD.org, Kris Kennaway <kris@obsecurity.org> Subject: Re: Lock order reversals in sys_pipe.c Message-ID: <XFMail.20020327165145.jhb@FreeBSD.org> In-Reply-To: <20020326224745.GF93885@elvis.mu.org>
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On 26-Mar-2002 Alfred Perlstein wrote: > * Alfred Perlstein <alfred@FreeBSD.org> [020326 14:43] wrote: >> * Kris Kennaway <kris@obsecurity.org> [020324 14:26] wrote: >> > The bento cluster is now running with WITNESS enabled to try and track >> > down some odd UMA lock corruption panics. Instead, it found the >> > following lock order reversal in sys_pipe.c overnight: >> > >> > Mar 24 09:02:29 <user.crit> gohan13 kernel: lock order reversal >> > Mar 24 09:02:29 <user.crit> gohan13 kernel: 1st 0xd99d6500 pipe mutex @ >> > /local0/scratch/usr/src/sys/kern/sys_pipe.c:450 >> > Mar 24 09:02:29 <user.crit> gohan13 kernel: 2nd 0xd971cddc process lock @ >> > /local0/scratch/usr/src/sys/kern/kern_sig.c:2093 >> > >> > Those source references are from a -current kernel from last night. >> >> Are you %100 on that? How did you get this to happen? >> >> I can see where I hold the pipe lock, then try to get a proc lock, >> but not the other way around... >> >> Any ideas? > > Note that I can pretty trivially fix this by dropping the pipe lock > while calling pgsigio in pipeselwakeup(), however I will then have to > make sure the callers of pipeselwakeup() can deal with someone else > mucking with the pipe during the call. > > Anyhow, wtf doesn't witness print out at least one instance of the > old locking? Basically let me know where locking is happening in > the other direction? That's easy to achieve. Add a static lock ordering in the compiled in arrays, then it will let you know when you do the other way. It may be an indirect relationship and not a direct one as well. The allproc/filedesc thing was an instance of indirect relationships determining the order. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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